The present invention relates to the input of information into a computer and, more particularly, to an instrument for interacting with a trackpad type navigational device for inputting information.
Trackpad type navigational devices for controlling movement of a pointer on a display screen are now relatively common. These navigational devices typically have a surface which is to be contacted by a human finger. Movement of the finger on the surface controls movement of the pointer. Many portable computers incorporate a trackpad navigational device as an integral part thereof.
Different trackpad navigational devices of the trackpad type operate on different electrical principles to sense movement of a human finger. For example, some rely on capacitance, others rely on the disturbance or distortion of an electric field, and others on the finger causing conductors to contact, etc. All of such devices, though, rely on the electrical properties provided by the human as manifested in the human finger and on contact over an extended surface area as is provided by a fingertip. Trackpad navigational devices generally sense the full fingertip but then calculate the centroid of the finger for their operation. In other words, the fingertip is translated into a single point of contact.
Although many say theoretically they are not limited to the pointer being a human finger, as a practical matter only those which are not activated by a simple touching of the pad surface by any conductor are widely used. There simply are too many instances in which a conductor accidentally may be brought into contact with the pad surface to make those responsive to any conductive touching practical.
Most computers which rely on the trackpad navigational devices to control movement of a pointer on a display screen typically include a program for "accelerating" the motion. As a finger moves faster on the pad surface, for example, this movement is interpreted as directing the pointer to move further on the screen than is indicated by the distance through which the finger moves. In other words, the relationship between finger movement on a pad surface and the resulting movement of a pointer on a screen is nonlinear.